Set a seed to keep test_smooth_non_linearities from flaking (#3253)

Summary:
Pull Request resolved: #3253

This test has been failing in OSS. It doesn't fail for every seed, but I was able to reproduce the failure with some seeds. Setting the seed to 0 makes it pass.

Reviewed By: dme65

Differential Revision: D98313699

fbshipit-source-id: 790dcf2fcfc1d25a00eaa12dd244c27c8ae576fb

Author: esantorella

test/utils/test_safe_math.py

@@ -285,6 +285,7 @@ def test_log_mean_exp(self):
 
 class TestSmoothNonLinearities(BotorchTestCase):
     def test_smooth_non_linearities(self):
+        torch.manual_seed(0)
         for dtype in (torch.float, torch.double):
             tkwargs = {"dtype": dtype, "device": self.device}
             n = 17